Conventionally, electrospinning (electric charge induced spinning) is known as a method for manufacturing filamentous substances (hereinafter referred to as “nano-fibers”) made of polymeric substances and having a diameter in a submicron scale.
In the electrospinning method, solution in which polymeric substances are dissolved (dispersed) in solvent is discharged (injected), to a manufacturing space, through a needle nozzle to which a high voltage is applied, so that nano-fibers can be obtained. More specifically, as the solvent of the solution which is charged by a high voltage evaporates, charge density increases. When Coulomb force acting oppositely generated in the solution exceeds the surface tension of the solution, the solution undergoes a phenomenon in which the solution is explosively stretched into filament (electrostatic explosion). The electrostatic explosion is repeated in the manufacturing space, thereby manufacturing nano-fibers made of polymeric substances with a submicron diameter.
A thin film having three dimensional structure of three dimensional mesh can be obtained by depositing nano-fibers manufactured by the above method on a substrate, and a highly porous web (nonwoven fabric) having submicron mesh can be manufactured by forming this film thicker.
Such web manufactured by the electrospinning method has been applied to a filter, a separator for use in a battery, a polymer electrolyte membrane or an electrode for use in a fuel cell, or the like, due to its high porosity made of pores in nano order and high surface area, and expected to achieve high performances.
Conventionally, as a method for manufacturing a practical web made of nano-fibers by manufacturing a large amount of nano-fibers, an apparatus has been proposed which manufactures the web by having a plurality of nozzles arranged in parallel and depositing a large amount of nano-fibers (see Patent Reference 1, for example).    Patent Reference 1: Japanese Unexamined Patent Application Publication No. 2002-201559